1. Technical Field
The present invention relates to a piezoelectric device in which a plurality of piezoelectric elements is arranged in parallel, a liquid ejecting head including the piezoelectric device, and a liquid ejecting apparatus.
2. Related Art
A liquid ejecting apparatus is an apparatus which includes a liquid ejecting head and ejects various types of liquid from the liquid ejecting head. As an example of such a liquid ejecting apparatus, there is an image recording apparatus such as an ink jet type printer or an ink jet type plotter, and recently, the liquid ejecting apparatus has been applied to various types of manufacturing apparatuses for the characteristic thereof that a very small amount of liquid can be landed accurately on a predetermined position. For example, the liquid ejecting apparatus has been applied to a display manufacturing apparatus which manufactures a color filter such as a liquid crystal display, an electrode forming apparatus which forms an electrode for an organic electro luminescence (EL) display, a field emission display (FED), or the like, and a chip manufacturing apparatus which manufactures a bio chip (biochemical element). A recording head of the image recording apparatus ejects ink of a liquid type, and a color material ejecting head for the display manufacturing apparatus ejects a solution of each color material of R (Red), G (Green), and B (Blue). In addition, an electrode material ejecting head for the electrode forming apparatus ejects an electrode material of a liquid type, and a biochemical organic substance ejecting head for the chip manufacturing apparatus ejects a bio organic substance solution.
The liquid ejecting head described above includes a plurality of pressure chambers and a piezoelectric device which generates the pressure fluctuation in liquid inside each pressure chamber. The piezoelectric device is configured to have a vibration plate which divides one side of the pressure chamber (for example, a side opposite to a nozzle plate on which nozzles are formed) and a piezoelectric element formed in every pressure chamber on the vibration plate. Here, as a piezoelectric element, it is known that the piezoelectric element is configured with, for example, in an order from a side close to the vibration plate, a lower electrode which functions as a common electrode with respect to a plurality of the pressure chambers, a piezoelectric body which is formed in every pressure chamber, and an upper electrode which functions as an individual electrode (for example, Japanese Patent No. 4321552). In addition, a part of a piezoelectric body layer sandwiched between the upper electrode layer and the lower electrode layer is a function portion (active portion) which is deformed by applying a voltage to both electrode layers.
The liquid ejecting head disclosed in Japanese Patent No. 4321552 is formed to have a thickness of a region between the adjacent two piezoelectric elements which is thinner than a region of the piezoelectric element in the lower electrode formed throughout a plurality of piezoelectric elements. Further, in the liquid ejecting head, a recess portion is formed on a boundary part with the piezoelectric element in the lower electrode in the region between the adjacent two piezoelectric elements. According to this configuration, a displacement characteristic can be improved by the piezoelectric element. Moreover, in the piezoelectric element disclosed in Japanese Patent No. 4321552, in order to prevent deterioration of characteristic of the piezoelectric body, a moisture resistance protective film is formed on a taper portion of the piezoelectric body layer.
In the piezoelectric device disclosed in Japanese Patent No. 4321552, if the recess portion formed on a lower electrode is formed to be deeper, a displacement characteristic is further improved. However, in the piezoelectric device disclosed in Japanese Patent No. 4321552, there is a problem in that improvement of the displacement characteristic is less likely to be improved. It is because that if the recess portion formed on a lower electrode which is a common electrode is formed to be deeper, the lower electrode is separated and troubles occur in driving.